The invention relates to a method of and to an apparatus for generating electric signals which are indicative of one or more parameters of a flow of comminuted material, and more particularly to a method of and to an apparatus for generating electric signals which denote the mass flow of fibrous material in a rod making machine of the tobacco processing industry.
Fibrous materials which can be monitored in accordance with the method and in the apparatus of the present invention include fragments of natural, reconstituted and/or substitute tobacco, or filaments or other forms of fibers which can be used as filters for tobacco smoke. Such fibrous materials are normally processed in so-called rod making machines, including machines for the making of cigarettes or other rod-shaped smokers' articles and machines for the making of rod-shaped filters which can be subdivided into filter rod sections of desired length.
Fibrous material which is to constitute the rod-like filler of a cigarette, cigar, cigarillo, cheroot or another rod-shaped smokers' product, or the material which is to constitute the rod-like filler of a filter for tobacco smoke, contains two constituents or fractions, namely a solid fraction and a liquid fraction. The solid fraction consists of dry tobacco and additives (such as flavoring agents) or of solid filter material, and the liquid fraction normally contains or consists of water. The liquid fraction of fibrous material which is to be converted into the filler of a filter rod can also contain one or more liquid chemicals, e.g., softening agents (such as triacetin).
It is already known to ascertain the entire mass flow of a tobacco stream or filter stream (hereinafter referred to as tobacco stream with the understanding, however, that the same procedure can be resorted to for the monitoring of streams which contain filter material for tobacco smoke), e.g., by resorting to X-rays, to beta rays or to other penetrative radiation. The intensity of radiation which has penetrated through the fibrous material is monitored for the purpose of generating a signal which can be utilized to adjust the mass flow of tobacco if the intensity of the thus ascertained signal departs from a preselected optimum value.
It is further known to ascertain the moisture content of a tobacco stream and to process the resulting signal with the signal denoting the entire mass flow of the stream in order to ascertain the mass flow of solid fraction of the tobacco stream. The thus obtained signal can be utilized to regulate the formation of a rod-like tobacco filler for the purpose of maintaining the mass flow of the solid fraction at a substantially constant value.
Thus, in order to obtain a signal which is indicative of the mass flow of solid fraction of a tobacco stream, it is necessary to resort to a source of penetrative radiation (which can be put to use only by observing numerous stringent regulations concerning the utilization of X-rays, beta rays or similar rays), and it is thereupon necessary to process the thus obtained signals with signals denoting the mass flow of the liquid fraction in order to obtain a signal which can be said to denote the mass flow of solid fraction of the tobacco stream.